1. Field of the Invention
The present invention relates generally to a looped one-wavelength loop antenna having a length equivalent to one wavelength related to communication, and, more particularly, to an improvement in a one-wavelength loop antenna for inhibiting the influence of a feeding cable on communication.
2. Description of the Related Art
A one-wavelength loop antenna is known, which includes a looped antenna element having a length equivalent to one wavelength related to communication and a feeding cable for feeding current to a feeding point on the antenna element. Such a one-wavelength loop antenna is in popular use. A technique for inhibiting the influence of the feeding cable on communication in such a one-wavelength loop antenna is proposed. For example, a balun-incorporated loop antenna is provided by applying such a technique. According to the technique, a loop conductor formed on a board has a balance/unbalance transformer formed on the same board to be located at one front end of the conductor at a feeding point and the balance/unbalance transformer cancels out current leaking out from the outer conductor of a coaxial cable serving as a feeding cable to inhibit the influence of current on communication.
According to control by the conventional technique, however, radiation of current from the feeding cable cannot be sufficiently canceled out, so that the influence on communication is not sufficiently inhibited. For this reason, development of a one-wavelength loop antenna that inhibits the influence of the feeding cable on communication has been in demand.